There are many characteristics of tissue products such as bath and facial tissue that must be considered in producing a final product having desirable attributes that make it suitable and preferred for the product's intended purpose. Improved softness of the product has long been one major objective, and this has been a particularly significant factor for the success of premium products. In general, the major components of softness include stiffness and bulk (density), with lower stiffness and higher bulk (lower density) generally improving perceived softness.
While enhanced softness is a desire for all types of tissue products, it has been especially challenging to achieve softness improvements in uncreped throughdried sheets. Throughdrying provides a relatively noncompressive method of removing water from a web by passing hot air through the web until it is dry. More specifically, a wet-laid web is transferred from the forming fabric to a coarse, highly permeable throughdrying fabric and retained on the throughdrying fabric until dry. The resulting dried web is softer and bulkier than a conventionally-dried uncreped sheet because fewer bonds are formed and because the web is less compressed. Thus, there are benefits to eliminating the Yankee dryer and making an uncreped throughdried product. Uncreped throughdried sheets are typically quite harsh and rough to the touch, however, compared to their creped counterparts. This is partially due to the inherently high stiffness and strength of an uncreped sheet, but is also due in part to the coarseness of the throughdrying fabric onto which the wet web is conformed and dried.
Moreover, from a manufacturing perspective, the throughdrying process is relatively energy intensive and therefore expensive compared to wet pressing. The high temperatures required for the throughdrying process also detrimentally affects the useful life of fabrics used in the manufacturing process.
Therefore, what is lacking and needed in the art is a method for manufacturing tissue products having improved softness, and in particular throughdried tissue products having improved softness, as well as a more economical method for manufacturing throughdried tissue products.